Doors are typically made from two molded or flush door skins attached to opposite sides a central door frame. The door facings are often molded from a wood fiber and resin compound, although fiberglass resin formed polymer door facings are known. The door frame typically includes stiles and rails made of wood located around the perimeter of the door. The interior of the door may optionally include a core.
Manual assembly of doors is relatively labor intensive, expensive, and subject to quality variations. During manual assembly, a door facing is placed on a production table with its intended exterior surface face down. Adhesive is then applied to the stiles and rails of a frame. The adhesively coated frame parts are then placed on the door facing on the table. Adhesive applied to a second side of the stiles and rails faces upwardly and a second door facing is placed with its exterior surface face upon the second side of the frame. The resulting assembled door is stacked at a holding station so that additional doors may be assembled. The assembled doors should be handled carefully, given that the components of the door can easily shift during transportation.
Each successive door assembly is stacked on top of the previous door assembly until a predetermined quantity of door assemblies has been stacked. The stack of door assemblies is then transported to and loaded in a press. The press applies pressure to the entire stack for a period of time sufficient to allow the adhesive to bond the door facings to the frame. Conventional adhesives, such as polyvinyl acetate, may take approximately thirty minutes or more in-press before the door reaches “green” strength. The door achieves green strength when the adhesive has reached sufficient bonding strength to hold the door components together for further handling.
Once an acceptable green strength is achieved, the doors may be removed from the press and moved to an in-process inventory until the adhesive reaches maximum cure strength. Depending on the adhesive used, the doors may need to remain in inventory for a relatively long period of time, for example two hours or more, or even as long as twenty-four hours, before the adhesive reaches maximum bonding strength.
After reaching maximum cure strength the doors are then moved to a final processing station. Final processing includes edge trimming the doors to customer specification and optional coating and/or painting of door skins and exposed edges of the stiles and rails around each door perimeter. Using this process, manufacturing time for a door may be twenty-four hours or more, from the time production is initiated to the resulting finished door is complete.